1. Field of the Invention
The present invention relates to packing assemblies for use in effecting fluid sealing around the wash pipe of a rotary drilling swivel and to such an assembly for effecting sealing around a rotating shaft of a pump.
2. Description of the Prior Art
In the drilling of oil and gas wells, a drill bit is rotated in a borehole by means of a string of drill pipe. The drill pipe is rotated on the surface mechanically by a rotating table mounted on a drilling platform or by a hydraulic motor, commonly referred to as a top drive. As is common in such oil and gas well drilling, drilling fluid or mud is circulated through the drill pipe and the drill bit to cool the drill bit and remove the cuttings, which are then recirculated to the surface and removed from the drilling fluid so it can be reused. Particularly in the case of deep wells, the drilling fluid can be at pressures that can range to several thousand psi.
The rotary drilling swivel commonly used in the drilling of oil and gas wells provides rotating support for the drill string suspended from it and a sealed passageway for circulating drilling fluids into the drill string. The drill pipe is in open-flow communication with a wash pipe, through which the drilling fluid flows, the wash pipe usually being stationary. A packing assembly forming part of the swivel rotates with the drill pipe, and is in scaling engagement with the wash pipe to prevent loss of drilling fluid out of the swivel assembly.
As noted above, depending on the depth of the well and/or well condition, drilling fluid pressure can reach several thousand psi, and at these high pressures, conventional, prior art packing assemblies used to seal between the wash pipe and the rotary head to which the drill pipe is secured have reduced life, resulting in leaking. Additionally, in top drive applications wherein the swivel assembly is rotating at a height of from 50 to 60 feet above the rig floor during drilling, it is difficult to maintain or adjust the packing or to add lubrication to the packing. Accordingly, only periodically, and typically only once a day, will the drilling operation be stopped to allow some adjustment to the rotating packing assembly and/or the addition of lubricant, which can be added through a grease port in the portion of the gland of the packing assembly that contains the seal rings.
Pumps employing rotary shafts, e.g., centrifugal pumps, generally employ lip types seals that are generally in a stacked configuration and employ various types of spacers or back-up rings, an adjustable gland being used to force the lips of the seals into engagement with the stuffing box or the like in which the seals are carried and the rotating shaft that extends through the stuffing box. In many cases, these pumps are in environments where change-out of the seal rings is difficult and results in costly downtime.